After weeks of debate about the theoretical and abstract dangers of fake news, there’s finally a concrete incident to discuss. On Sunday, a North Carolina man walked into Comet Ping Pong, a pizzeria in an affluent corner of Northwest D.C. wielding an assault rifle, which he fired at least once.

The man, 28-year-old Edgar Maddison Welch, told police he intended to “self-investigate” a bogus story alleging that Hillary Clinton was running a pedophilia ring out of the restaurant. The story, dubbed, deplorably, “Pizzagate” has spread around certain fake news circles, culminating in Welch’s expedition to Comet on Sunday.

So much of the discussion about “fake news” has involved vague questions about, for example, whether Russian-backed propaganda could have been a factor in Donald Trump’s victory. A big Washington Post report suggested that Russia had played a role in spreading lots of fake news; Adrian Chen, among others, convincingly argued that one major basis for that report was extremely fraught. There’s a broader question of the extent to which a foreign power could influence the election, and the extent to which that would really be anything new. Jack Shafer suggests not.

But the Comet incident offers a disconcerting example of what looks like a concrete result of fake news leading to violence. BuzzFeed’s Craig Silverman last month offered an excellent forensic tracing of how the story came about. A white-supremacist Twitter account falsely claimed on October 30 that emails showed a pedophilia ring centered around Clinton. It jumped from there to message boards, and then to bogus news sites. Eventually, the Patient Zero Twitter account passed along the bogus posts as affirmation of his tip, even though the story originated with him anyway. The connection to Comet came because the restaurant’s owner popped up in emails with Clinton campaign chair John Podesta discussing a fundraiser. Those emails were hacked and then leaked during the election by an unknown actor, though U.S. intelligence officials have said they believe Russia is behind the hacks.

The “Pizzagate” story goes beyond some of the other bogus claims made during this election. “Random D.C. pizza parlor is the home of an international pedophilia ring run by the former first lady and Democratic nominee for president” wouldn’t pass muster at The Onion, to say nothing of less reputable, less entertaining satire sites. Yet Welch is not alone. The New York Times reported in November that one other person had already shown up to investigate, presumably without a high-powered firearm. There were death threats and hundreds of social-media posts.

The gullibility involved in the case is disheartening, and the recourse to weapons is scary. But the more frightening problem is that there’s no promising solution to the causes that produced the showdown in Chevy Chase on Sunday. Most suggestions for fighting back boil down, as Shafer notes, to some form of censorship, which is an unacceptable path.

Nor is the traditional press in a position to make much difference. There’s a long list of overlapping theories, some valid and some not, for the weakened position of the traditional press, but whatever the truth, it’s not structurally prepared to fight this sort of thing. The barriers to entry for media outlets, including the bogus ones that spread the Pizzagate story, are extremely low, while traditional outlets can no longer maintain any sort of oligopoly on distributing news, so that the emergence of fake news stories is unstoppable. The press can debunk them, of course, and in fact it has done an admirable job—as Silverman’s piece and another in the Times did. But this makes little difference. The audiences that are receptive to those debunkers are the ones who would have missed the original fake story anyway, and the ones who believe the fake story are inclined to dismiss mainstream reports out of hand, so the debunkers won’t influence them either.

It would be helpful if responsible citizens would do all they could do to stifle stories like this. But that hasn’t always been the case. Retired General Michael Flynn, a former head of the Defense Intelligence Agency who Trump has named as his national security adviser, helped spread one of the early stories about a pedophilia ring that Silverman identified:

One major proponent of the Pizzagate story has, unsurprisingly, been InfoWars, Alex Jones’s clearinghouse for wild-eyed conspiracy theories. Trump has courted Jones, appearing on Jones’s radio show and praising him.

The technique of raising a completely bogus idea and then demanding that its critics debunk it—by proving a negative—is a favorite technique of conspiracy theorists, and more recently it’s become a favorite technique of the Trump team.

Here’s how the post-truth sausage gets made. The president-elect, for example, will moot the idea that there were millions of illegal votes cast in the election, despite overwhelming evidence that the claim is false and no evidence it is true. His defenders will, nonetheless, then demand that the people who think vote fraud is false prove it is false. By the end of the week, Reince Priebus—the chairman of the GOP, Trump’s chief of staff-designee, and one of the mainstream, establishment members of his team—can go on national network television and say he doesn’t know for sure whether millions of illegal voters cast ballots, and that “it’s possible.”

The allegations against Welch are interesting because they follow the archetypal narrative of Islamist terrorism self-radicalization. A young man begins reading on the Internet; over time, he comes to believe mainstream sources that are questionable, misleading, or downright false; eventually, he decides to arm himself and take matters into his own hands on behalf of a political cause.

Just as authorities continue to struggle with how to stop self-radicalized Islamist terrorists, it seems inevitable that there will be more incidents like the one on Sunday. Already, at least one fake-news site is positing that the whole episode was a false-flag operation designed to facilitate a crackdown on purveyors of fake news. Across the country, some number of people are reading the story and nodding in agreement. Some of them might even decide to pick up a gun and do something about it.

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David A. Graham is a staff writer at The Atlantic, where he covers U.S. politics and global news.